A screening machine is provided with a screening device and a screening device with multiple adjacent screen shafts disposed rotatable each of which being provided with a plurality of screen disks. The screen disks are made of rigid materials and are separated from one another in the axial direction by a clearance each. The screen disks of a screen shaft engage in clearances of the screen disks of adjacent screen shafts. Half of the screen disks are provided with a cleaning device for cleaning the clearances between the screen disks.